Abstract:

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The mechanism of the degradation process of nickel based superalloy CM247LC under
creep loading was analyzed by considering the microscopic chemical composition of the material
such as phase boundary of γ and γ’ phases.
In this study, a Directionally Solidified (DS) nickel-based superalloys CM247LC was used as test
specimens. The creep test was performed at 900oC under an uni-axial stress of 216 MPa. Each
specimen was creep ruptured and interrupted at different hours and then analyzed.
The change of chemical composition around the interface analyzed precisely by used Auger
Electron Spectroscopy (AES). It was found that the local enrichment or lack of cobalt and
chromium was found at the interface. This tendency was not found in the stress free area. Since
chromium is the well-known element that dominates the degradation of this material, such an
enrichment or lack of cobalt and chromium may play an important role for forming a crack
propagation path near the interface. This local segregation should be analyzed further to make clear
degradation mechanism of this material.

Abstract: In the present paper, the non-equilibrium grain-boundary segregation of P atom was
studied in low alloy steels subjected to a low tensile stress at different temperatures. The AES
(Auger electron spectroscopy) experiments and dynamic analyses were conducted to study on the
non-equilibrium grain-boundary segregation of P atom. The research results show that
non-equilibrium segregation of phosphorus occurred at the grain boundaries of the steels
2.25Cr1Mo and 12Cr1MoV, while the critical time reached about 0-1 hour at constant temperatures
773 and 813K. The relationship between the diffusion rate and the diffusion time for the complex
and the phosphorus atom was investigated based on the experimental results. Eventually the
diffusion coefficients of complex and P were calculated with using a proposed dynamic model.

Abstract: The cold roll B-added Ti-IF steel is annealed for different times at 810 oC. The microstructure development is studied by Optical Microscope（OM） and the concentration of boron and phosphorus segregation at grain boundary is measured by Auger electron spectroscopy（AES）. The result shows that the grain of the cold- rolled sample is elongated along the rolling direction and the elongated grains become into equi-axis shape after annealing 60 to 180sec. Boron and phosphorus segregated at gain boundaries. But boron’s concentration at grain boundary is higher than that of phosphorus and increase from 5at.% or so to about 10at% after annealing 150sec, Then boron’s concentration decrease slowly to 8at.% at 240sec. While phosphorus’s concentration increase to the max of 2.5at.% or so at 120sec, then its concentration decrease to 1at.% or so after annealing 240sec.

Abstract: ZrNi intermetallic compound is used in several application fields due to its very favorable characteristics for the storage of hydrogen. The hydrogen reactions are important, it is vital to examine the evolution of physico-chemical properties at the surface. X-ray photoelectron spectroscopy, is used to follow the evolution of electronic properties of ZrNi versus the ion sputtering in ultra high vacuum in the range 300-600°C. Morever, the evolution of species concentrations at the surface of ZrNi in the range 100-700°C is followed by means of Auger electron spectroscopy. The present results show that temperature and ion sputtering favor significant changes in surface properties of ZrNi. In situ annealing of ZrNi favors the oxygen decontamination associated with segregation of zirconium metal on the surface. The values of binding energies deduced from the reconstruction of XPS spectra, allowed the identification of species present at the surface. The results indicate that nickel is not contaminated and all the obtained sub-oxides are related to bonding states of oxygen with zirconium (Zr2O, ZrO, ZrO2 and Zr2O3). The ion sputtering of the surface of ZrNi causes preferential sputtering phenomenon. The later results from the removal of surface layers and from the appearance of zirconium oxide layers initially present on the surface. The results obtained by AES show the segregation of impurities (oxygen and carbon) and of zirconium on the surface of ZrNi. AES observations of Zr segregation start to be important above 300°C and this is in agreement with XPS analysis showing a Zr enrichment of the surface of ZrNi.

Abstract: The inertial friction welding of similar PM FGH96 superalloy was investigated. The inertial friction welding introduced steep thermal gradients of welding zone for PM FGH96 superalloy, the whole welding process only needed several seconds, therefore, it’s a fast heating and cooling completely recrystallization process. Dramatic changes in the microstructure were observed over a narrow weld zone, which across the weld interface was measured to be about 1.0-1.2mm. Significant changes in the secondary and tertiary γ′ distribution can be observed over the first 2mm from welding line, while very fine tertiary γ′ particles precipitated in a unimodal size distribution and in a high density at welding line. The fine secondary re-precipitated γ′ under fast cooling was spherical in shape, which gradually transformed into elliptical, cube with the distance from welding line. No significant texture or grain distortion was observed in the extensively plastically deformed region due to recrystallization.